WATER SUPPLY 



Springs and Wells. It has been roughly 

 estimated that of the quantity of rain fall- 

 ing on the earth, about one-sixth is absorbed 

 by the soil, a similar portion is carried 

 away by rivers, c., and the remainder is 

 re-evaporated. Springs are either shallow 

 or deep seated, and arise from the natural 

 overflowing of subterranean reservoirs of 

 water. They are of different characters, 

 either pure or mineral, cold, hot, and even 

 boiling, being dependent on the source 

 from whence they come. 



Wells are of two kinds, ordinary, or very 

 deep wells; the latter being also termed 

 Artesian, from their having been first used 

 at Artois, in France. These two sources 

 are well illustrated by a section of the 

 London basin, from the north to the south 

 of the Thames, and they depend entirely 

 on the permeable and non-permeable cha- 

 racter of the strata comprised within that 

 area. Thus the ordinary or shallow wells 



around London are formed by sinking into the sand and gravel, (as shown at a a) which from 

 their permeable nature become more or less charged with water, which is retained therein as 

 in a reservoir by the retentive nature of the thick bed of London clay immediately below it. 

 In the other case, that of Artesian wells, the water supply is derived from an entirely 



Rules for finding Springs. Mr. Swindell, in his work on Wells, mentions the following j 

 grass assume a brighter colour in one particular part of a field than in the remainder, or if whe 

 found beneath it. In summer, the gnats hover in a column and remain always at a certain he 

 dense vapours arise from those portions of the surface from which, owing to the existence of su 

 the morning and evening. The Springs to which these rules apply are only such as are near tl 

 but to execute such operations with a chance of success, a certain knowledge of elementary G< 



DRAINAGI 



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Soils may be divided into three varieties ; 1, the porous soil, as sand, gravel, &c.; 2, the retentive 

 or impervious, as clay, marl, dense locks, &c.; 3, the mixed or partly porous, as loam, soft chalk, 

 and surface soils of mixed ingredients ; according to the relative positions of these several 

 strata, so will the mode of drainage vary. 



The general principles of land drainage may be exemplified by the four diagrams here shown. 

 In the first diagram, we have an illustration where the soil immediately beneath that forming 

 the surface is porous, the next stratum retentive, underlaid by the mixed variety. In this case, 

 the drains must either be made with regard to the porous soils only, without interference with 

 the clay; or the main drains must be made completely through the clay, which should be bored 

 in the lowest or wettest places; this will bring the land into a much drier condition. Where 

 the retentive soil lies uppermost, as represented in the second diagram, with the porous soil 



LONDON: PUBLISHED BY J 



